The real reason why folks on Wall Street care about what's going with SAC is because the hedge fund is a major player when it comes to generating revenue for brokerage firms.

The brokerage business depends on trading volume. It doesn't matter whether a stock is going up or down. It's about the amount of shares being traded. That's because brokers earn commission for each share traded. A broker could make anywhere from half a penny per share or five cents a share.

According to Bloomberg, SAC is one of the biggest clients for Morgan Stanley and Goldman Sachs. The fund has also been a client for prime brokerage services to JPMorgan, Credit Suisse and Barclays, the report said.

Not only does Wall Street support the fund's stock and derivatives trades, but the firm is also a reliable client for those further down the food chain, like technology equipment providers. Now, the fund's banks face an uncomfortable choice. Should they keep acting as a broker to SAC Capital? There will be strong temptation to maintain full ties with the fund. The payments from SAC Capital are welcome during these leaner times on Wall Street. And banks may be reluctant to drop a client that has not yet been proved guilty.

Cohen started SAC in 1992 with $25 million AUM. Today the hedge fund behemoth employs about 900 people globally.